1. Field of the Invention
This invention pertains to stops for limiting the relative motion between a gyroscope and a structure to which the gyroscope is pivotably mounted, and more particularly to such limit stops which prevent tumbling of the gyroscope when contact between the gyroscope case and the limit stop occurs.
2. Description of the Prior Art
Gyroscopes, or gyros as they are sometimes called, are widely used in navigation systems because of their ability to maintain a fixed axis in space when mounted pivotably to a structure which changes its orientation in space. In such applications the gyro is mounted in gimbals and will maintain its spin axis direction regardless of the orientation of the structure to which it is attached. In some missile applications it is desirable that the gyro mounting only allow limited relative movement between the gyro spin axis and the missile structure. This is usually accomplished by mounting limit stops near the gyro so that when a non-spinning portion of the gyro case approaches and contacts the limit stop the spin axis will be slewed by the limit stop to assume a new orientation in space.
In general, when a gyro hits a limit stop, precession forces tend to move the gyro tangent to the limit stop surface at the point of contact. Since the limit stop in a missile usually forms a closed curve such as a circle or square, the gyro precessing tangent to the surface begins a very rapid and violent traversal of the limit stop. When this occurs, the gyro is said to tumble and it may require an appreciable length of time before it can recover from the tumble and again be usable. In particular, the gyros in some guided missiles will tumble when the gyro contacts a limit stop and will at that instant abort the mission.
If it is desired to slew the gyro spin axis at an extra fast rate, it is necessary either to apply extra large precessional forces to the gyro or to mechanically cage the gyro during the slewing maneuver. Both of these methods have disadvantages. Excessively large amplifiers and other electronic equipment are required to supply the large currents needed by precession coils to produce large precession forces, and mechanical caging requires additional mechanisms as well as additional time for the caging and uncaging cycles. The non tumbling limit stop of this invention prevents gyro tumbling and at the same time enables high slew rates of the gyro spin axis by using normal precessional forces and frictional contact forces to produce a mechanical super cage.